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Query: UMLS:C0018801 (heart failure)
 72,216 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Apoptosis of cardiac muscle cells contributes to the development of cardiomyopathy. Recent studies showed that insulin-like growth factor I (IGF-I) inhibits apoptosis of cardiac muscle cells and improves myocardial function in experimental heart failure. This study was carried out to elucidate the role of phosphatidylinositol 3-kinase (PI 3-kinase) in the anti-apoptotic actions of IGF-I in cardiomyocytes and to explore whether expression of constitutively active PI 3-kinase can inhibit apoptosis in cardiomyocytes. Apoptosis of primary cardiomyocytes was induced by doxorubicin treatment and serum withdrawal. Transduction of cardiomyocytes with constitutively active PI 3-kinase specifically lead to serine phosphorylation of Akt, whereas phosphorylation of IGF-I receptor, IRS1/2 and p44/42 mitogen-activated protein kinase were not increased. In the cardiomyocytes transduced with constitutively active PI 3-kinase, activation of the pro-apoptotic caspase 3 was attenuated and fragmentation of DNA was reduced. Preincubating cells with PI 3-kinase inhibitor LY294002 was associated with loss of anti-apoptotic actions of IGF-I and PI 3-kinase. Neither IGF-I nor constitutively active PI 3-kinase lead to serine phosphorylation of Bad, suggesting that the anti-apoptotic effects of PI 3-kinase are not mediated through Bad phosphorylation in cardiac muscle cells. To determine whether activation of caspase 3 is sufficient to induce apoptosis in cardiomyocytes, an engineered TAT-caspase 3 protein was introduced to cardiomyocytes. Significant reduction of cell viability occurred in the cardiomyocytes transduced with active caspase 3, indicating that activation of caspase 3 is sufficient to cause cardiomyocyte death. These findings indicate the existence of an IGF-I receptor-PI 3-kinase-caspase 3 pathway in cardiomyocytes that plays an important role in the anti-apoptotic actions of IGF-I in heart. Moreover, these data suggest that modulation of PI 3-kinase activities may represent a potential therapeutic strategy to counteract the occurrence of apoptosis in cardiomyopathy.
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PMID:Expression of constitutively active phosphatidylinositol 3-kinase inhibits activation of caspase 3 and apoptosis of cardiac muscle cells. 1100 72

Cardiac hypertrophy often leads to heart failure and is associated with abnormal myocardial adrenergic signaling. This enlargement of myocardial mass can involve not only an increase in cardiomyocyte size, but increased proliferation of cardiac fibroblasts. A potential key player in the cardiac hypertrophic response is the ERK family of MAPKs. To gain mechanistic insight into adrenergic regulation of myocardial mitogenic signaling, we examined beta-adrenergic receptor (beta-AR) stimulation of ERK activation and DNA synthesis in cultured adult rat cardiac fibroblasts, including the involvement of tyrosine kinases in this signaling pathway. Addition of the beta-AR agonist isoproterenol (ISO) to serum-starved cells induced DNA synthesis in a dose-dependent manner, and this was inhibited by selective inhibitors of the epidermal growth factor receptor (EGFR). Importantly and in agreement with the involvement of MAPKs and the EGFR in this response in cardiac fibroblasts, the EGFR inhibitor AG1478 attenuated ISO-induced ERK phosphorylation. Moreover, pretreatment with PP2, a selective inhibitor of the Src tyrosine kinase, attenuated both ISO-mediated EGFR phosphorylation and ERK activation. Furthermore, studies in these cardiac fibroblasts showed that phosphatidylinositol 3-kinase contributed to beta-AR-mediated ERK activation, but not to EGFR activation. Finally, studies using selective inhibitors of matrix metalloproteases indicated that they and heparin-bound EGF shedding were involved in beta-AR-induced ERK activation and subsequent DNA synthesis in cardiac fibroblasts. Because these cells primarily express the beta(2)-AR subtype, our findings indicate that beta(2)-AR-mediated EGFR transactivation of intracellular tyrosine kinase signaling pathways is the major signaling pathway responsible for the adrenergic stimulation of mitogenesis of cardiac fibroblasts.
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PMID:Beta-adrenergic receptor-mediated DNA synthesis in cardiac fibroblasts is dependent on transactivation of the epidermal growth factor receptor and subsequent activation of extracellular signal-regulated kinases. 1204 15

We investigated whether insulin resistance in patients with chronic heart failure (CHF) is associated with impaired insulin signalling in skeletal muscle and whether exercise training would lead to an improvement in insulin signalling, concomitant with enhanced insulin action. Fourteen men with CHF due to idiopathic dilated cardiomyopathy, with mild-to-moderate limitation of physical activity and a left-ventricular ejection fraction of less than 45 %, were studied before and after either a 5 month exercise training programme (n = 7) or standard care (n = 7). Seven healthy men participated as controls. Whole-body insulin-stimulated glucose uptake was determined by the euglycaemic hyperinsulinaemic clamp technique and skeletal muscle biopsy samples were obtained before and after the insulin infusion for insulin signalling measurements. Insulin-stimulated glucose uptake was 20 % lower in CHF patients versus healthy subjects. Physiological hyperinsulinaemia increased tyrosine phosphorylation of insulin receptor substrate (IRS)-1 by approximately 2.5-fold, IRS-1-associated phosphatidylinositol 3-kinase (PI-3-kinase) activity by approximately 2-fold and Akt (protein kinase B) phosphorylation by approximately 3-fold, with similar responses between healthy subjects and CHF patients. Insulin-mediated glucose uptake was not altered in patients after standard care, whereas exercise training elicited a 25 % increase in glucose uptake. Neither standard care nor exercise training altered insulin-stimulated tyrosine phosphorylation of IRS-1, IRS-1-associated PI-3-kinase activity or Akt phosphorylation. In conclusion, the CHF patients demonstrated impaired insulin-stimulated glucose uptake, despite normal signal transduction in skeletal muscle at the level of IRS-1, PI-3-kinase and Akt. Of clinical relevance is the finding that exercise training improves glucose uptake. However, these changes in insulin action after exercise training appear to be independent of enhanced insulin signalling at the level of IRS-1, PI-3-kinase or Akt.
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PMID:Insulin signalling and resistance in patients with chronic heart failure. 1274 Apr 26

Insulin resistance has been described in several diseases that increase cardiovascular risk and mortality, such as diabetes, obesity, hypertension, metabolic syndrome, and heart failure. Abnormalities of insulin signaling account for insulin resistance. Insulin mediates its action on target organs through phosphorylation of a transmembrane-spanning tyrosine kinase receptor, the insulin receptor (IR). Several mechanisms have been described as responsible for the inhibition of insulin-stimulated tyrosine phosphorylation of IR and the IR substrate (IRS) proteins, including proteasome-mediated degradation, phosphatase-mediated dephosphorylation, and kinase-mediated serine/threonine phosphorylation. In particular, phosphorylation of IRS-1 on serine Ser612 causes dissociation of the p85 subunit of phosphatidylinositol 3-kinase, inhibiting further signaling. On the other hand, phosphorylation of IRS-1 on Ser307 results in its dissociation from the IR and triggers proteasome-dependent degradation. Dysregulation of sympathetic nervous and renin-angiotensin systems resulting in enhanced stimulation of both adrenergic and angiotensin II receptors is a typical feature of several cardiovascular diseases and, at the same time, is involved in the pathogenesis of insulin resistance. The characterization of molecular mechanisms involved in the pathogenesis of insulin resistance may help to design efficacious pharmacologic molecules to treat endothelial and metabolic dysfunction associated with insulin resistance states to reduce the cardiovascular risk and to ameliorate the prognosis of patients with cardiovascular diseases.
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PMID:Insulin resistance and cardiovascular risk: New insights from molecular and cellular biology. 1683 60

Under normal physiology, insulin exerts vasodilatory and pro-survival actions via the phosphatidylinositol 3-kinase (PI3-kinase) pathway and vasoconstrictive and mitogenic actions via the mitogen-activated protein kinase (MAPK) pathway in the vasculature. In the insulin resistant states, insulin signals through the PI3-kinase pathway are blunted but its signals through the MAPK cascade remain intact. This imbalance predisposes insulin resistant patients to hypertension and atherosclerosis. The renin-angiotensin system (RAS) is expressed both systemically and locally in the cardiovascular system. Insulin resistance up-regulates the local RAS which contributes to the pathogenesis of hypertension, heart failure, and atherosclerosis. Angiotensin II impairs insulin signaling, induces inflammation via the NF-kappaB pathway, reduces nitric oxide availability and facilitates vasoconstriction, leading to insulin resistance and endothelial dysfunction. Thus the RAS, insulin resistance and inflammation perpetuate each other and coordinately contribute to endothelial dysfunction, vascular injury and atherosclerosis. RAS inhibition decreases cardiovascular and renal morbidity and mortality and the incidence of new onset Type 2 diabetes.
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PMID:Angiotensin II and insulin crosstalk in the cardiovascular system. 1721 73

Cardiac hypertrophy is promoted by adrenergic over-activation and represents an independent risk factor for cardiovascular morbidity and mortality. The basic knowledge about mechanisms by which sustained adrenergic activation promotes myocardial growth, as well as understanding how structural changes in hypertrophied myocardium could affect myocardial function has been acquired from studies using an animal model of chronic systemic beta-adrenoreceptor agonist administration. Sustained beta-adrenoreceptor activation was shown to enhance the synthesis of myocardial proteins, an effect mediated via stimulation of myocardial growth factors, up-regulation of nuclear proto-oncogenes, induction of cardiac oxidative stress, as well as activation of mitogen-activated protein kinases and phosphatidylinositol 3-kinase. Sustained beta-adrenoreceptor activation contributes to impaired cardiac autonomic regulation as evidenced by blunted parasympathetically-mediated cardiovascular reflexes as well as abnormal storage of myocardial catecholamines. Catecholamine-induced cardiac hypertrophy is associated with reduced contractile responses to adrenergic agonists, an effect attributed to downregulation of myocardial beta-adrenoreceptors, uncoupling of beta-adrenoreceptors and adenylate cyclase, as well as modifications of downstream cAMP-mediated signaling. In compensated cardiac hypertrophy, these changes are associated with preserved or even enhanced basal ventricular systolic function due to increased sarcoplasmic reticulum Ca(2+) content and Ca(2+)-induced sarcoplasmic reticulum Ca(2+) release. The increased availability of Ca(2+) to maintain cardiomyocyte contraction is attributed to prolongation of the action potential due to inhibition of the transient outward potassium current as well as stimulation of the reverse mode of the Na(+)-Ca(2+) exchange. Further progression of cardiac hypertrophy towards heart failure is due to abnormalities in Ca(2+) handling, necrotic myocardial injury, and increased myocardial stiffness due to interstitial fibrosis.
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PMID:Cardiac hypertrophy induced by sustained beta-adrenoreceptor activation: pathophysiological aspects. 1738 10

The central role of phosphatidylinositol 3-kinase (PI3K, p110alpha) signaling in allowing cancer cells to bypass normal growth-limiting controls has led to the development of PI3K(p110alpha) inhibitors. A challenge in targeting PI3K(p110alpha) relates to the diverse actions of the PI3K pathway in numerous cell types. Recent findings in mice deficient in PI3K(p110alpha) activity in the heart, demonstrate the critical role of this pathway in protecting the heart against pathological insults. Mice deficient in PI3K(p110alpha) displayed accelerated heart failure in response to dilated or hypertrophic cardiomyopathy. These results help explain the association of cardiomyopathy in cancer patients given tyrosine kinase inhibitors and raise concerns for the use of PI3K(p110alpha) inhibitors in cancer patients with cardiovascular risk factors. Interestingly, an inhibitor of the mammalian target of rapamycin (a downstream effector of PI3K), did not have adverse effects on the heart. A more complete understanding of the complex arms and interactions of the PI3K pathway will hopefully lead to the development of anti-cancer agents without cardiac complications.
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PMID:PI3K(p110alpha) inhibitors as anti-cancer agents: minding the heart. 1740 10

An inexorable loss of terminally differentiated heart muscle cells is a crucial causal factor for heart failure. Here, we have provided several lines of evidence to demonstrate that mitofusin-2 (Mfn-2; also called hyperplasia suppressor gene), a member of the mitofusin family, is a major determinant of oxidative stress-mediated cardiomyocyte apoptosis. First, oxidative stress with H(2)O(2) led to concurrent increases in Mfn-2 expression and apoptosis in cultured neonatal rat cardiomyocytes. Second, overexpression of Mfn-2 to a level similar to that induced by H(2)O(2) was sufficient to trigger myocyte apoptosis, which is associated with profound inhibition of Akt activation without altering ERK1/2 signaling. Third, Mfn-2 silencing inhibited oxidative stress-induced apoptosis in H9C2 cells, a cardiac muscle cell line. Furthermore, Mfn-2-induced myocyte apoptosis was abrogated by inhibition of caspase-9 (but not caspase-8) and by overexpression of Bcl-x(L) or enhanced activation of phosphatidylinositol 3-kinase-Akt, suggesting that inhibition of Akt signaling and activation of the mitochondrial death pathway are essentially involved in Mfn-2-induced heart muscle cell apoptosis. These results indicate that increased cardiac Mfn-2 expression is both necessary and sufficient for oxidative stress-induced heart muscle cell apoptosis, suggesting that Mfn-2 deregulation may be a crucial pathogenic element and a potential therapeutic target for heart failure.
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PMID:Mitofusin-2 is a major determinant of oxidative stress-mediated heart muscle cell apoptosis. 1756

Recent advances in molecular imaging have permitted the noninvasive imaging of apoptosis, a critical process underlying the pathogenesis of many diseases of the cardiovascular system including atherosclerotic vascular disease, myocardial ischemia and reperfusion injury, chronic heart failure, myocarditis, and cardiac allograft rejection. Multiple molecular targets including phosphatidylserine, phosphatidylinositol 3-kinase, and caspases have been targeted by a variety of imaging agents and modalities such as nuclear scintigraphy, PET, MRI, and fluorescent and bioluminescent imaging. Translationally, methods utilizing radiolabeled annexin V have proven promising in several clinical trials of ischemia-reperfusion injury and cardiac allograft rejection. New approaches using novel molecular imaging agents show great potential for the ability to image apoptosis in the research and clinical setting. Ultimately the ability to detect apoptosis noninvasively would help to identify patients for emerging anti-apoptotic therapies and guide clinical management with the aim of maximal myocardial preservation.
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PMID:Noninvasive imaging of apoptosis in cardiovascular disease. 1807 26

Titins, giant sarcomere proteins with major mechanical/signaling functions, are expressed in 2 main isoform classes in the mammalian heart: N2B (3000 kDa) and N2BA (>3200 kDa). A dramatic isoform switch occurs during cardiac development, from fetal N2BA titin (3700 kDa) expressed before birth to a mix of smaller N2BA/N2B isoforms found postnatally; adult rat hearts almost exclusively have N2B titin. The isoform switch, which can be reversed in chronic human heart failure, alters myocardial distensibility and mechanosignaling. Here we determined factors regulating this switch using, as a model system, primary cardiomyocyte cultures prepared from embryonic rats. In standard culture, the mean N2B percentage initially was 14% and increased by approximately 60% within 1 week, resembling the in vivo switching. The titin isoform transition was independent of endothelin-1-induced myocyte hypertrophy and was not altered by pacing, contractile arrest, or cell stretch; however, it was modestly impaired by decreasing substrate rigidity and strongly dependent on serum components. Angiotensin II significantly promoted the transition. The mean N2B proportion in 1-week-old cultures dropped 20% to 25% in hormone-reduced medium, but addition of 3,5,3'-triiodo-l-thyronine (T3) nearly restored the proportion to that found in standard culture. This T3 effect was not prevented by bisphenol A, a specific inhibitor of the classic genomic pathway of T3 action. In contrast, the titin switch could be stalled by the phosphatidylinositol 3-kinase inhibitor LY294002, which decreased the proportion of N2B mRNA transcripts within hours and suppressed a rapid T3-induced increase in Akt phosphorylation. Also, angiotensin II, but not endothelin-1 or cell stretch, enhanced Akt phosphorylation. Thus, although matrix stiffness modulates developmental titin isoform transitions, these transitions are mainly regulated through phosphatidylinositol 3-kinase/Akt-dependent signaling triggered particularly by T3 via a rapid action pathway.
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PMID:Thyroid hormone regulates developmental titin isoform transitions via the phosphatidylinositol-3-kinase/ AKT pathway. 1809 19


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